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104 lines
4.0 KiB
Markdown
104 lines
4.0 KiB
Markdown
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[](https://github.com/marketplace/actions/arduino_ci)
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[](https://github.com/RobTillaart/PCA9685_RT/blob/master/LICENSE)
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[](https://github.com/RobTillaart/PCA9685_RT/releases)
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# PCA9685_RT
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Arduino library for I2C PCA9685 16 channel PWM extender
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# Description
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This library is to control the I2C PCA9685 PWM extender.
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The 16 channels are independently configurable in steps of 1/4096.
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This allows for better than 0.1% finetuning of the duty-cycle
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of the PWM signal.
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The PWM's of the different channels have individual start and stop moments.
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This can be used to distribute the power more evenly over multiple servo's
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or give special effects when used in an RGB LED.
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The frequency of the PWM can be set from 24 to 1526 according to the datasheet, however in practice not all frequencies are set accurate.
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Lower frequencies do better than higher frequencies.
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## Interface
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### Constructor
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- **PCA9635(deviceAddress)** I2C address
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- **begin()** initializes the library after startup. Mandatory.
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- **begin(sda, scl)** idem, ESP32 ESP8266 only. Library does not support
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multiple Wire instances (yet).
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- **reset()** resets the library to start up conditions.
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- **isConnected()** checks if address is available on I2C bus.
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### Mode
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- **writeMode(reg, mode)** configuration of one of the two configuration registers.
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check datasheet for details.
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- **readMode(reg)** reads back the configured mode, useful to add or remove a
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single flag (bit masking)
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### PWM
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- **setPWM(channel, ontime, offtime)** The chip has 16 channels to do PWM.
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The signal is divided in 4096 steps, 0..4095.
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The pulse can begin =**ontime** on any step and it can stop on any step =**offtime**.
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This allows e.g. to distribute the power over the 16 channels, e.g. the
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channels do not need to start at the same moment with HIGH.
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- **setPWM(channel, offtime)** simple PWM that always start on **ontime = 0**
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- **getPWM(channel, ontime, offtime)** read back the configuration of the channel.
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- **allOFF()** switches all PWM channels OFF. **Experimental** in 0.3.0
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To "undo" the allOFF one can call the **reset()** function and set all
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PWM channels again.
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- **digitalWrite(channel, mode)** mode = HIGH or LOW, just use the PCA9685 as
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a digitalpin.
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This single function replaces the setON() and setOFF() that will become
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obsolete in the future.
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### Frequency
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- **setFrequency(freq, int offset = 0)** set the update speed of the channels.
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This value is set the same for all channels at once.
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- **getFrequency(cache = true)** get the current update frequency of the channels.
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This is same for all channels. If cache is false, the frequency is fetched and
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calculated from the **prescaler** register and will probably differ from the
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value set with **setFrequency()**.
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The frequency is constrained to be between 24 and 1526 Hz.
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As the frequency is converted to an 8 bit **prescaler**,
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the frequency set will seldom be exact.
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After changing the frequency, one must set all channels (again),
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so one should set the frequency in **setup()**
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The parameter offset can be used to tune the **prescaler** to get a frequency
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closer to the requested value. See **PCA9685_setFrequency_offset** example.
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Default the offset = 0. As the prescaler is smaller at higher frequencies
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higher frequencies are less accurate.
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Making offset too large can result in very incorrect frequencies.
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When using offset, the **getFrequency(false)** will return the adjusted prescaler.
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### Misc
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- **lastError()** returns **PCA9685_OK = 0** if all is OK, and
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| Error code | Value | Description |
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|:----|:----:|:----|
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| PCA9685_OK | 0x00 | Everything went well
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| PCA9685_ERROR | 0xFF | generic error
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| PCA9685_ERR_CHANNEL | 0xFE | Channel out of range
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| PCA9685_ERR_MODE | 0xFD | Invalid mode register chosen |
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| PCA9685_ERR_I2C | 0xFC | PCA9685 I2C communication error
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# Operation
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See examples
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